3D Shadows as physical invariant. 3D shadows have been introduced by Hau et al. in [1]} as a phyiscal invariant to verify genuine objects in a 3D point cloud scene and detect object spoofing attacks. In object spoofing attacks [2]}, [3]}, [4]}, [5]}, point cloud measurements are injected into a scene to spoof objects that are then erroneously detected by 3D-object detectors used by AVs. Shadow-Catcher [6]} detects such attacks by using the bounding box of objects generated by object detectors to identify a shadow region behind the detected object and inspects that shadow region for presence of point cloud measurements, which are indicative of a spoofing attack. The authors have shown that 3D shadows are a strong physical invariant that can be used to verify genuine objects. In this work, we explore searching the scene for void regions and attributing them to genuine objects.
